A United Nations official called the suffering of people in the Gaza Strip “absolutely horrible”, as Israel continued pummeling the crowded, blockaded territory in retaliation for the deadly weekend incursion by Hamas, the armed Palestinian organization that controls the enclave.

Water and electricity have been cut off, Adnan Abu Hasna, the media adviser for the U.N. agency that helps Palestinian refugees, said in a phone interview from Gaza City. The only power plant in Gaza shut down Wednesday because the blockade enforced by Egypt and Israel has prevented shipments of fuel.

Hospitals were running short on fuel to keep backup generators running, he said, compounding fears of a humanitarian disaster as patients pour in for treatment amid Israeli airstrikes that have killed hundreds. And without reliable electricity, residents had no means of storing food.

“We are facing a huge disaster”, - he said.